This application claims the priority of Application No. 103 06 152.5 filed in Germany on Feb. 14, 2003, the disclosure of which is expressly incorporated by reference herein.
The invention relates to an internal-combustion engine having balancing shafts. Preferred embodiments relate to engines having four cylinders in a V-arrangement, a crankshaft, and a first balancing shaft parallel to and below the crankshaft for reducing the free inertial forces of the second order.
An internal-combustion engine in a V-arrangement is known from German Patent Document DE 42 38 148 A1. A balancing shaft is provided for reducing the free inertial forces of the second order. In the further text, this is called the first balancing shaft. The first balancing shaft extends below the crankshaft parallel thereto. This first balancing shaft is driven by way of a chain drive, a planetary gear being provided for reversing the rotating direction.
The first balancing shaft contributes to the smooth running of the internal-combustion engine. However, it is problematic that, as a result of the spatial position of the first balancing shaft—laterally offset with respect to the crankshaft—, the free inertial forces of the second order are not completely eliminated.
It is therefore an object of the invention to construct an internal-combustion engine with four cylinders in the V-arrangement, in the case of which the free inertial forces of the second degree are completely eliminated.
This object is achieved according to certain preferred embodiments of the invention by providing an internal-combustion engine having four cylinders in a V-arrangement, having a crankshaft and having a first balancing shaft for reducing the free inertial forces of the second order which is arranged below and parallel to the crankshaft, wherein a second balancing shaft is provided in a point of intersection of the cylinder Vs above the crankshaft, and wherein the rotation center points of the first balancing shaft, of the second balancing shaft and of the crankshaft are situated on a perpendicular axis of symmetry which extends through the point of intersection.
Further advantageous features of preferred embodiments of the invention are described herein and in the claims.
The invention provides a second balancing shaft which is arranged in the point of intersection of the cylinder-Vs above the crankshaft. Here, the rotation center points of the first balancing shaft, of the second balancing shaft and of the crankshaft are situated on a perpendicular axis of symmetry which extends through the point of intersection. In other words: The first balancing shaft is situated precisely below the crankshaft, and the second balancing shaft is situated precisely above the crankshaft.
In a further development of the invention, it is provided that the second balancing shaft is provided with a main lubricant duct. It is known that, in the case of an internal-combustion engine in a V-arrangement the main lubricant duct is situated in the cylinder V. By way of this main lubricant duct, the main bearings of the crankshaft and the spraying nozzles for the piston cooling are supplied with lubricant. In the case of this embodiment, the second balancing shaft additionally takes over the function of the main lubricant duct. For this purpose, the second balancing shaft has a lubricant feeding device, a guiding duct in the interior, outlet openings for the removal of the lubricant and eccentric weights.
In a further development, the second balancing shaft has partial milled-out sections on the circumference. A tube is arranged in the interior as a guiding duct.
As a result of the ideal position of the two balancing shafts, the free inertial forces of the second order are completely eliminated. Since the second balancing shaft additionally takes over the function of the main lubricant duct, no additional space is required. The weight increase in comparison to the internal-combustion engine known from the state of the art is moderate.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.